Stator windings of an electric rotary machine where the temperature has risen due to an AC copper loss due to energization or a DC copper loss due to leakage flux are required to be cooled.
Therefore, a spreading method is used as an inexpensive cooling method. This method is that coil ends of windings are cooled by applying oil stored at a position higher than an outer bottom surface of a rotor that is spread by a rotation of the rotor.
An example of spreading method is disclosed in the Japanese Patent Application Laid-open Publication No. 2014-072921, for example.
Techniques disclosed in the Publication No. '921 are as follows.
An electric motor includes a stator fixed to a motor housing, and a rotor disposed so as to face radially inward with respect to the stator.
The rotor is formed by sandwiching both end faces of a rotor core by a pair of retaining plates.
In each of the retaining plates, a plurality of first oil catchers and second oil catchers protrude in an axial direction on end faces on sides not in contact with the rotor core, respectively.
Each of the oil catchers extends linearly in a radial direction to near a vicinity of an outer peripheral edge from a vicinity of an inner peripheral edge of the retaining plate.
As the rotor rotates, the oil catchers hold the oil in the motor housing, and can splash the oil in a rotational direction of the rotor.
However, oil spreading parts (oil catchers) that can splash the oil by the rotation of the rotor are formed so as to extend in a radial direction in the technology disclosed in the Publication No. '921.
Further, the oil catchers protrude in the axial direction and have sectional shapes such that variations of irregularities are large.
Thus, there is a problem that efficiency of the electric rotary machine is reduced due to an increased rotational resistance of the rotor.